\begin{figure}[tpb]
\begin{center}
  \includegraphics[width=1\textwidth]{figures/active-node-step}
\end{center}
\caption{Steps to process a \pput request in \sys using active
  storage. W1 and W2 are witness nodes. Note that steps 1 to 4
  are executed in the same group of nodes, but for clarity, we
  separate these steps in two figures. }
\label{fig:active-node-steps}
\end{figure}



